Not Applicable.
Power presses are built in a wide variety of styles and sizes to perform a variety of functions, such as stamping, drawing, forming and many others. The deleterious effect of impact loading associated with many functions of power presses is well known and recognized. A variety of cushion arrangements for use in power presses is well known. Examples of such cushion arrangements associated with power presses are taught in: U.S. Pat. No. 4,732,033, entitled, xe2x80x9cPneumatic Die Cushion,xe2x80x9d issued Mar. 22, 1988, to Smedberg, et al.; U.S. Pat. No. 4,736,615, entitled, xe2x80x9cPneumatic Press Counterbalancexe2x80x9d, issued Apr. 12, 1988, to Smedberg, et al.; U.S. Pat. No. 4,796,460 entitled, xe2x80x9cCushion Construction Including Snubberxe2x80x9d, issued Jan. 10, 1989, to Smedberg, et al; U.S. Pat. No. 4,825,681, entitled, xe2x80x9cPneumatic Press Counterbalance and Cushion Constructionxe2x80x9d, issued May 2, 1989 to Smedberg, et al.; U.S. Pat. No. 4,860,571, entitled, xe2x80x9cPower Press With Improved Cushioning Systemxe2x80x9d, issued Aug. 29, 1989, to Smedberg, et al; and U.S. Pat. No. 4,930,336, entitled, xe2x80x9cSingle Action Cylinderxe2x80x9d, issued Jun. 5, 1990, to Smedberg, et al.
Though cushioning improves operation of a power press, it is still necessary to provide a means to modulate the force applied by a press ram to work piece and stationary portions of the press to reduce further the deleterious effect of undesired shock loading on parts of the press and to achieve a smooth application of force to a work piece.
The herein disclosed invention provides an improved power press. This press construction provides improved holding of a work piece and generates an improved desirable loading in a power press. An improved force modulator is used to hold the work piece and to regulate the internal loading in the press having a ram moveable relative to a stationary part of the press. The force modulator includes a vessel with hydraulic fluid contained in the vessel. A hydraulic fluid container is mounted within the vessel. One end of the force modulator is connected to the press ram. An opposite end of the force modulator is connected to the stationary part of the power press. A regulator is connected to the container to control the flow of hydraulic fluid into the vessel thereby determine a back force on the press ram congruent with a defined force displacement curve, that is, the defined force for each incremental ram position in response to the position of the ram relative to the stationary part of the press. The back force on the press ram substantially eliminates undesirable impact loading on parts of the press and achieves a smooth application of a working force to a work piece positioned in the press.